‘Star clusters – groups of stars that are bound together by gravity – might act like black-hole “nurseries”, providing an ideal environment to grow generations of black holes, ‘ explained Dr Davide Gerosa from the University of Birmingham, lead author of a paper on the cosmic kindergartens.

‘But in order to know what type of star clusters are most likely to be capable of producing these, we first need to know something about the physical conditions that would be needed.’